>>7708656A facebook page, email, and a bank account is all you need for running a group of like a hundred. Some core members to keep the games running even if the main big boy is not around. I don't know your area procedures for registered communities.
One game mode I like has many names, but it goes like this: Everybody starts off in the same place, GM calls a minute or so for everybody to disperse. After the time has passed, it is game on, and a free-for-all. When you're hit, you stay there and count to ten. Done so, you lift up both your arms, and anybody can come and tap you onto their team. It most often ends up with one big team who are still shooting each other, but it is good, fast fun.
Picture; Nerf version WHEN?